A lower bound for the spectral radius of a digraph |
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Authors: | E Gudiño |
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Institution: | Departamento de Matemáticas, Universidad Simón Bolivar, Caracas 1080-A, Venezuela |
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Abstract: | We show that the spectral radius ρ(D) of a digraph D with n vertices and c2 closed walks of length 2 satisfies Moreover, equality occurs if and only if D is the symmetric digraph associated to a -regular graph, plus some arcs that do not belong to cycles. As an application of this result, we construct new sharp upper bounds for the low energy of a digraph, which extends Koolen and Moulton bounds of the energy to digraphs. |
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Keywords: | 05C35 05C50 05C90 15A18 |
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